An interior part of an automobile, for example, a door trim, is manufactured by a surface skin being welded to the surface of a base made of resin material. The welder used for this welding is one that uses a jig that is exclusively used for the welding of the object to be processed and is designed to match the shape of the object (for example, see Patent Document 1).
Also, available is a welder, such as a horizontal sliding welder that performs in turn the setting and the welding of the object to be processed by the use of two jigs provided on a sliding mechanism and a rotary welder that performs in turn the setting and the welding of the object to be processed by the use of two jigs provided on a turntable mechanism.    Patent Document: Publication of the Laid-open Application, Publication No. 2000-202913